The relative growth of Austinixa patagoniensis (Rathbun, 1918), a symbiotic crab inhabiting burrows of the callianassid shrimp Callichirus major (Say, 1818) in Balneário Camboriú beach, Santa Catarina (26º59'S, 48º39'W) was studied in 119 juveniles, 228 males and 249 females. Functional regressions were used to describe the relative growth of the following variables: carapace length and width, abdomen width, maximum height and length of the upper and lower margins of the propodus of the left chelipod. Carapace width (CW) was used as the reference dimension. Excepting the height of the propodus of juveniles and the upper length of the chelae of females whose relative growth was described by a linear model, all variables were better described by the traditional potential model. Results of the analysis showed that morphological changes detected during the ontogeny of A. patagoniensis are related to reproduction. The occurrence of transition points in the chelae and abdomen growth indicates that the species matures in Balneário Camboriú at 7,8-7,9 mm (males) and 7,9-8,3 mm (females) of carapace width. The same values were found also for the species in Cassino beach, Rio Grande do Sul (32°13'S, 52°15'W), where the species is associated to another host, the callianassid shrimp Sergio mirim (Rodrigues, 1971). Therefore, it is suggested that the size at maturity of A. patagoniensis does not vary between hosts and latitude (at least between the studied limits), in spite of the differences observed in maximum attained sizes, fecundity and reproductive behavior of the two sites.
Allometry; Brachyura; sexual maturity
